Stabilized oscillation generator



Dec. 6, 1949 w. H. Buss 2,490,404

STABILIZED OSCILLATION GENERATOR Filed Jan. 7, 1947 2 Sheets-Sheet 1 9 wim/70N af awr /Wz caf/25mm Puffs INVENTQR Dec 6, 1949 w. H. Buss I STABILIZED OSGILLATION. GENERATOR 2 Sheets-Sheet 2 Filed Jan. '7, 1947 oo 0 o. moo. om

conc 0 one come oog ATTORNEY lll -Iln Patented IDec. 6, 194

STABILIZED OSCILLATION GENERATOR Warren H. Bliss, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 7, 1947, Serial No. 720,535

(Cl. Z50-36) Claims. 1

This application relates to oscillation generators and in particular, a generator the frequency of operation of which is stabilized but can be changed to any frequency within a given wide range.

There is great need of ra calibrated variable lfrequency master oscillator which can readily be set to any ypredetermined frequency within its range, with assurance th-at the output frequency will remain close to the desired preset frequency.

The general lobject of this invention is to provide oscillation generating means as outlined above f-or supplying to a transmitter or other utilization means, oscillations of any frequency within a given wide range.

A further object of the present invention is to provide oscillation generating means aS described above and simple means for setting or selecting the chosen frequency.

A further object of the present invention is to provide oscillation generating and selecting means wherein the oscillations generated and of a selected frequency iare fixed in frequency with respect to an oscillator of standard fixed frequency such as a crystal oscillator.

An additional object of the `pre-sent invention is to provide an oscillation generator as described above with simple and effective means for automatically stabilizing the frequency of operation thereof at any selected frequency.

The above objects are attained as follows:

Oscillations from the standard frequency source (divided in frequency) are used to establish time intervals of xed and known duration and also to produce voltage fof a duration measured by ysaid time intervals. At the start of certain of the time intervals, a preset cycle counter is set into operation to count o a preset number of cycles of the oscillations generated and stop. A voltage of duration measured by the counting time of the cycle counter is developed and the differential of said produced voltage and developed voltage is used to control the master oscillator frequency.

Now if the generated oscillation :frequency is changed, and ya new number set up on the counter, my system takes over automatically from there on to stabilize this new frequency of operation. Thus a series of frequencies related as desired may be generated. Such operation is not possible in known systems wherein the fixed frequency dividers limits operation to one frequency only.

A system as -described above is shown and claimed in the copending Iapplication of Charles J. Young, Ser. No. 719,035, led December 28, 1946.

In the said Young system, the time intervals of fixed duration are measured by the voltage peaks :produced iby 4and in xed frequency relation :with respect to the oscillations of the standard fre'- quency source. The same peak-s which initiate the said interval measurement also open a gate between the master oscillator and the cycle counter and permit vthe oscillations from the same to reach the cycle counter to be counted, thereby starting the time interval in which said count isto take place. Obviously, the master oscillation generator cycle may be at zero voltage at that instant and there will be some delay in time between the initiation of the counting interval and the rst count. Then the interval which is a measure of the count does not truly represent the lactual counting time and the control of the master oscillators frequency by said differential voltage is not as accurate as it could be.

A further object of my invention is to provide an improved means for measuring land comparing the .time intervals established by the standard frequency source and the time interval during which the count takes place, wherein, irre- Ispective of varying phase relations between the oscillations from the standard source and those from the controlled oscillation generator the differential potential used for control purposes is a true measure of the time it took to count 'off the pre-set number of cycles thereof. An object of my invention then is to provide means for causing the master oscillator control to be independent Ioi' phase relations between said oscillator output wave ,and oscillations' from the crystal -oscillator used asa standard of reference.

Briefly, these objects are attained in accordance with my invention by causing a frequency divider to measure off time intervals of fixed duration and .produce voltage pulses which are a measure of said time intervals as in the said Young disclosure. However, here the counter is not started immediately -by the peak voltages from such frequency divider. On the contrary, la time delay is introduced in this operation. Then the counter is started and counts olf a pre-set number 'of cycles out of the master oscillation generator. A lpulse is developed which starts when the counter starts and ends when the counter has finished the count. 'Ilhis pulse is then compared with the first mentioned voltage pulse. Because of the time delay introduced between the start of the intervals from the standard source and the time at which the count takes place, the first mentioned pulse measuring the standard intervals starts ahead of the second produced pulse measuring the counting time while the latter pulse continues for a time after the end of the first pulse. The overlapping of the two pulses is variable depending upon the relative phases of the currents and on their relative frequencies and the pulses yare compared in the differential correction circuit to produce corrective potentials, the relative lengths of which depend on whether the frequency cf the master oscillator is above or below the frequency of the standard source. These pulses are then used to correct the frequency of the master oscillator as in the Young case so that by roughly tuning the master oscil-A lator frequency by a condenser and by setting up the desired number on a frequency divider or counter, there is immediately 4supplied to the transmitter or other utilization circuit oscillations of any one of a very wide range of frequencies. The two pulses are opposed to cancel the overlapping portions ,to leave two voltages representing the time delay before the count starts, the other the time used to complete the count after the pulse representing the standard interval ends. Any variations of the Vphase of the oscillations from the controlled source relative to these from the standard source wil-l cause similar changes in the durationof said two voltages thus canceling out the effect thereof. 'Ilhese voltages are then combined (in effect) to provide the control potential.

In describing my invention in detail, reference will be made t the attached drawing wherein:

Eig. 1 illustrates by blockV diagram an oscillation generator :arranged in accordance with my invention for stable operation at any selected frequency of la wide range of frequencies.

Fig. 2 illustrates by voltage curves the operation `of my system of Figs. l and 3..

Fig. 3 illustrates details of the manner in which pulses, of fixed time separation, developed in unit S, control the cycle counter of unit 4 and the differential correction apparatus of unit 5 which is also controlled rby vthe counter to act through the reactanee tube o f unit 6 to stabilize the generator at any frequency selected for generation by setting the number of cycles counted and roughly adjusting the tuning condenser of the master oscillator. A'

Referring to Fig. l, the master oscillator 2, which supplies the output for use in, for example, a transmitter T, is shown as controlled from a frequency standard I. The frequency standard I may include a crystal oscillator. 'The basic control is obtained cmparing'two time intervals which are measured one by the standard oscillator l frequency,` the other being a measure of a preset number of cycles of the oscillations generated in unit 2. Byv way olf example, it may be assumedthat the frequency standard i operates at a frequency -of 1,090 cycles per second and the master oscillator 2 which' may be set and/or tuned at any one of any desired number of fre-` quencies, will, for purposes, of illustration, be operated at 7580 cycles per second. To obtain the two short time intervals which are compared to obtain control energy for controlling the frequency of operation of'oscillator 2, separate frequency dividers on time sensitive elements 3 and` 4 are used. Element is basically a fixed fre.- quency divider, such as a chain of multivibrators, which divides the frequency of the standard I, in the case illustrated by IML This meansthat the output of timer 3 will lhave aV frequency of ten cycles per second. In the embodiment described, the unit -3 is assumed to'include a divider of tion.

i the multivibrator or similar type and a wave shaper or peaker such as a differentiating network supplying output of a repetition rate of ten pulses per second as illustrated by line a of Fig. 2.

|Ihe second frequency divider which is in unit 4 is in the embodiment described essentially an electronic counter with an adjustable stop set which stops the count thereof as set. A counter o f this type is shown in the copending Grosdolf U. S. application Serial #580,446, led March 1, 41,945, and in the aforesaid Young S. applica- It is the purpose of this frequency divider in unit 4 to count olf a predetermined number of cycles of operation of the master oscillator in unit 2 and at the end'of this counting interval, to stop counting 'fand produce an output pulse d. In my illustration of the oscillator, operating at 7580 cycles per second, assume that the counter is set at the number 758. This means that if the master oscillator unit 2 is operating exactly on a frequency of 7580 cycles per second, the interval of time which frequency divider or counter 4 will measure will be equal to the length of time passed during 758 cycles or T16 second which is to be compared with the le second time intervals measured by timer 3,. The start of operation of counter 4 is initiated by a time delayed pulse generated by one of the pulses from counter 3, and counter 4 counts the preset number of cycles or pulses from the master oscillator of unit 2 and stops.

The differential correction control 5 compares the fixed intervals of time measured by the timer 3 with those measured by counter 4 and produces a corrective voltage, representing the difference of the intervals, which is applied to an oscillator frequency control means in'unit El which may be, by Way of illustration, a reactance tube per se well known in the art. Lines e and j of Fig. 2 show opposed voltage pulses measured by a standard interval of time which pulses are obtained in the correction control unit 5 from the frequency divider 3 output pulses line b and lines g and h showl voltage pulses produced in the correction control 5 of 4duration measured by the output pulses from frequency divided 4. The initiation of the time intervals lshown in lines .fl and I L is produced by alternate pulses, line a, here comme .from the .frequency divider s but delayed in time as indicated byline b .of Fig. 2, Termination oi the intervals shown in lines g and h is produced by the pulses of line d, `coming from the frequency divider 4. The voltage curves illustrate a case where the oscillator in unit 2 operates at too low a frequency and the pulses, lines y and h, are of longer duration than the pulses, lines e and f, because it took the counter more than of al second to Vcount the preset number. To obtain the control voltage, the correction control circuit 5 in effect, adds algebraically the voltages represented by lines e and h and the voltages represented by lines f and g. These combined or added voltages are shown in lines i and i. The pulse. 2,9 and its complementary pulse 29 are shorter in time duration than the pulse 30 and itsv complementary pulse 3 0', providing a resultant voltage f or correction purposes which in the case illustrated, is used to raise the frequency of the master oscillator in unit 2. If the frecuencias 'in mit 2 .and unit l are exactly as desired .SQ that, the preset. ,number can be Counted in unit 4 during the time intervals measured by the frequency divider 3, the pulses 29 and 30 are 0f like 'duration and r1.9 .cerrection takes place.

When the frequencies are not as desired, pulse 30.

standard pulses and counting pulses is usedv through reactance tube 6 to control the frequency of operation of the oscillator 2 in the proper direction to reduce the correction to zero, and to adjust the oscillator to the correction point of operation. In the embodiment described, I have provided means responsive to positive pulses only and therefore, in the correction operation, I make use of pulse 29 and pulse 30, lines i and i, respectively.

The relationship between the frequency of the standard I and the master oscillator in unit 2 can be adjusted or set at any desired value by means of dial switches associated with the frequency changer 4. In the case illustrated, the cycle counter dials are assumed to be set at 758 which would cause the master oscillator to operate at 7580 cycles per second. Adjusting the counter circuit in unit 4 changes the frequency of the oscillator as described above and its frequency may be changed practically continuously throughout a wide range merely by setting the frequency divider 4 as desired'and then roughly retuning the oscillator in unit 2 to the frequency selected. The oscillatory energy as selected in frequency is supplied to the transmitter l for use as desired.

The standard frequency oscillator in rectangle I may be conventional and many oscillators appropriate for use here are known in the prior art and the same will not be described in detail herein. The same remarks apply to the apparatus in rectangle 3. In practice, it takes the form of a frequency divider. The frequency divider may` carried out to provide pulse output as shown in i line a, Fig. 2. Many means are known in the prior art for shaping the waves as desired. For example, when the unit 3 is a multivibrator, its output is of square wave form and may be supplied to a diierentiating network to produce the peaks separated by the desired time intervals. A voltage dinerentiating network of this general type is shown in Fig. 1 of the copending Max Mesner application #559,469, filed October 19, 1944. The cbunter circuit in unit 4 is as stated above in general like that of the above referred to Grosdoif application, and is the same as the counter of the aforesaid Fig. 3 of Young application. The details of the circuit are not shown here. The differential correction control circuit of unit 5 wherein the pulses are compared as to time intervals is illustrated in detaill in Fig. 3. The reactance tube 6 and oscillator 2 may be conventional and in order to simplify the showing have not been included in Fig. 3.

In the illustrated form of the frequency divider 4, three sections are used. One counting units, a second tens and a third hundreds Switches are provided so that any number desired may be set up thereon and the frequency divider 4, when operated as described hereinafter, will serve tdy count olf that number of cycles generated by the generator in unit 2. associated therewith a three-pole, ten-position switches for setting the number to be counted and when the number is counted, the arrangement is such that the device .4 is returned to its original position and simultaneously sends out a pulse of energy which operates as described hereinafter. The oscillations are fed to the rst lsection in the cycle counter at lead 6| in Fig. 3 and the generated pulse at the end of the counting period appears on the lead 44 in Fig. 3.

As stated above, the oscillations or short pulses synchronized thereby are supplied from the oscillator to the input lead 6|, and at the electrode of a tube amplier therein is produced the potential which resets the device 4 when it has finished counting the preset number, and, also the potential supplied to lead 44 which goes to the differential correction control unit 5 to block the oscillator output as will appear in detail hereinafter, and terminate the counting time interval by returning certain multivibrator circuits to one condition of stability so that the cycle of operation may be completed and repeated. The arrangement for accomplishing this purpose and other purposes is shown in Fig. 3. In Fig. 3, the rectangle 5 includes the differential correction control and comprises in the embodiment shown, two locking stages MVI and MV2. In addition to the multivibrators MVI and MV2 are also provided, a locking stage MVS controlled by the locking stagev MVI and e, gating and voltage peaking stage GS controlled by the locking stage MV2. In practice, the wave peaking means and gating means which permits or prevents oscillations reaching the counter may be in the oscillator unit or as illustrated in Fig. 3 in separate units as at rectangle 5a which includes the Oscillation peaking means, a gate therefor and control means for the gate. The rectangle 6 includes the reactance tube while the rectangle 2 includes the master oscillator.

The pulses of line a are minus and are supplied by condenser 26 to the anodes and thence to the grids of the pair of tubes 45 and 48 in the locking stage MVI which are substantially conventional so that when one is drawing current, the other tube is cut oif and vice versa and the application of a negative pulse is ineffective on that tube having a negative grid but is effective on that tube having a positive grid to switch current therefrom to the other tube. The locking stage MVI has its second tube 48 anode coupled by a lcondenser 3i] to the control grid of the tube 49 in the locking stage MV3. This coupling includes an amplier tube 49 having its grid circuit coupled to condenser 3bA by a time delay network in the form of a resistor R and condenser C of values such as to ldelay pulse energy fed thereto from the tube 48 a selected interval, in the example given, 11-0 of the time interval measured by the peaks from timer 3 as shown in line b of Fig. 2. The anode of the tube 45 of locking stage MVI is connected by a resistor R6 to the control grid The different sections haveI reactants tube s. filter heinous 'Robes it and; narethe ogmhihtna tubes- Note that Since. tutosA 4 8, and. 5B are oohlillgtive and. hgh-aunque: tive respeetively. ih therost position, thehoteh: tialse. ahah at. theanodestbere.

areof opposed polarity-and are sooohibilled; to. supply. the notential i oillnei. Fle- 2;. The same... remarks apply. to tubes 45 and 5 6. andthe potontialsi and o at the anodes of tubes 4,5 and 5B which, are repre-V sented; in lines f` and g, in Fig. 2 and, combined provide the potential g represented in line.. i.. ot Fig. 2. The` arrangement. oftubes 6.6` and` 6,8 is. such that the positive. peaks only of lines i and 7': are elective on the. charge of the storage. condenser C2- of. networkrFN. The pulse. 29 makes tube Sit conductive to. let the condenser.. of discharge a small amount. The. pulse 30. acting on the. grid of tube 66 permits. the power. supply to add a small amount of charge. to the condenser.

C2 of EN, If 30 is larger. than 29. the charge gains as does thev potential at FN. yIn other words, the charge on C2 is proportional to the difference between the potentials 29 and 35 and this potential on condenser. C2 is supplied to the reactance tube` stage 6. The reactance tube stage is connected in a well known manner with the conventional oscillator in unit 2 to control its frequency of operation in accordance with the potential developedin C2, in this case, to increase the oscillator frequency.

The locking stage MVil` has the grid of tube 53 coupled to the anode of the amplifier tube bly condenser 50 and has the anode of this tube cou-` pled by condenser 5I to the control grid or'- a gating stage tube 55. Note that the controll grid of the tube 52 of the multivibrator stage is coupled by condenser 5K9 to the ca tlnoc'le of a cathode follower stage vtube CS whose control. grid is coupled by condenser 59'A to theanode of an amplifier Steef@ tube 6.3, the elld'o'f. which' is @selected to. the output lead 44 or the counter circuit rnitputz The anode o f tube 63i is alsocoupledby condenser 65 to the grid of the tube' 58 of the'locking 4stage MV2. Thus. a negative potential. (line d, 'Ele 2.) on the anode of tube 6 3vtrips stages and back to their s top positions if theyV navefbeen tripped therefrom. The potential onthe'cathode f tube CS' and hence 'ou the grid. of tutti?. 0i MVS is in phase with the potential at the anode of tube 63 because, tube CS is a athodehfollower stage. 'The anodeof the tube 55 ofthe locking circuitI MV3'is also coupled by condenser 5l to the vco f trol grid of the gating stage tube 55. The pur, pose of this` tube is to Dgrllitblooks of oscillatory energy from the oscillator 2 tobe passedthere-1 v threlleh and. Supplied. tothe Counter. ih unit t when the gate tube is'open and toblook off pase, sage of other blocks` of oscillationsowhen the gate tube is closed. When'tube 5,3 isoconductive, alow potential appears unitsv anode which causes the third grid of tube,V 5,5r tobe. a high negative ptential and alone. with the negative" patente! applied to the control grid by resistors 55 and 51', this tube'i's biased toont-'off normally, anode of the tube 55 is coupled by condenser 5,5" to the lead l running'to th'e first decade counter in the counter with'stop setin unit 4j The con-f trol grid of the tube 55 is connected by lead 5'( to the output of the controlled oscillator yin unit 2. A coupling and direct current blocking condenser CC is included in this lead. The anoder of the tube 55 is also coupled by condenser 55' and lead 6I to the grid in the tube 56 of the locking 'stage MW. This connection also includes a couplingV l suon that current flows in tubes 48, 56 and 5,3 as

indicated by the arrows adjacent said tubes. Current flowl iscut off in tubes 45, 58 and 52. Since current ows in tube 53 the potential at its. anode is down and the gating tube 55 is biased to cut off and no oscillations are supplied to the circuit in unit 4 by way of lead 6l. The oscillatory energy generatedl in the master oscillator in 2 isl however, continuously applied by lead 81 to theA rst grid in the gating circuit tube but is blookedtherein by the negative bias on the grids of this tube 5.5.

When a negative pulse of energy, such as represented in line a, is supplied from the output of the device 34 through the coupling condenser 26 to the control grids of tubes 45 and 48, this locking stage is tripped to its other position of stability at which current is cut off in tube 48 and flows in-tube 4.5. When this happens, the voltage at the anode of tube 48 represented by e on the lead thereto rises as shown in line e of Fig. 2

While the voltage designated f on the anode of tube 45 falls as represented by line f of Fig. 2. Now the cycle of operation has started and the voltages of fixed time duration measured by the pulses of xed frequency out of timer 3 are being developed by this multivibrator stage MV'I. At

the same time, the increasing pulses e at thek anode of tube 48 vare applied'through coupling condenser 50 and the time delay network RC to the. control grid of the tube 49, heretofore biased to cut-ou, to make the same produce a delayed pulse. The potential onA the anode of tube'49 falls to apply a negative pulse through the condenser 50 to the grid of the tube 53 of the locking stage MV3. This switches the current from tube 53 to tube 52 and flips the locking stage into its other condition of stability whereat the potential on the anode of tube 53 increases. This increase in potential is applied by coupling condenser 5| to the third grid in the gating tube 55V. The gating tube 55 which has heretofore been biased to cut off as stated above, nowl becomes conductive on the application of this positive peak. The tube 55 permits oscillations supplied by the generator in Aunit 2 to be amplied and peaked therein and fed by the condenser 55" and lead 6I to the input'of the device 4 and also by lead Blto the grid of tube 56 of stage MV2. The tube 55 being biased highly negative, operates in` a manner similar tothe operation of aA class C amplifier so that peaks only of the oscillatory energy are fed out of the anode thereof. These peaks are designated cV and are shown in line c of Fig. 2. The oscillatory energy supplied from the. oscillator to the rst grid inthe gate tube 55 is shown in line bb of Fig. 2 and is so designated on the lead to the grid of tube 55.

The device 4 starts its count to provide, after the set number of cycles has been counted, a posi# tive pulse which goes to the grid of tube 63. However, simultaneously, with the start of the operation 'of the device 4, the oscillations supplied from the anode of tube 55 via lead 6I4 and coupling condenser cc to the control grid of tube 56, being negative, linee, Fig. y2, trips this locking circuit Vl l named source in accordance with the `differential of the developed voltages.

L2. `In apparatus .for ,producing oscillatory energy Athe frequency of which may be set at any one vof numerous frequencies in a wide range of `frequencies in combination, a source of oscillatory energy of fixed frequency, a source of oscillatory Venergy of controllable frequency, means controlled by the source ofxed frequency for setting iup pulses of energy separated by time intervals `of fixed duration, a variable frequency divider, means set in .operation by said pulses for starting said variable frequency divider into operation to count oi ya preset number of cycles .of the oscillations generated and stop, means including va locking circuit for developing a voltage representative of said time delay, means including a second locking circuit for developing a voltage `representative of the time said variable frequency divider is operating after the ending of said ltime intervals of fixed duration, and means for ycontrolling the frequency .of said second named source Ain accordance with the differential of the developed voltages.

3. In apparatus for generating oscillatory energy of changeable frequency in combination, a vsource of oscillatory energy of xed frequency, -a source of oscillatory energy of controllable frequency, means controlled by said xed frequency vsource for producing pulses separated by predetermined time intervals of fixed duration, a variable frequency divider coupled to said controllable oscillation generator, means for Startiing said frequency `divider to Voperate a fraction of `a cycle .afterthe occurrence of selected ones of Said Ipulses for producing .an energy pulse after said controllable oscillator generates a preset number of cycles and stops, means for producing a first series of voltages measured by `said first time intervals, means for producing a second series of voltages measured by the operating periods of said frequency changer, means for .combining said volt-ages to cancel vout those parts of the rst and second :ser-ies of voltages which occur at the same time and leave two resultants, one of which represents the-time delay in starting said counter and the other of which represents the time between the end of selected ones of said time intervals and the end of said operating periods, means `forobtaining the differential of said two resultante and deriving therefrom a potential the polarity of which is determined by which resultant is of greatest duration, and means for controlling the frequency of said controllable source in accordance with said .resultant Y,

to thereby cause said resultante to have equal lengths.

4. In apparatus for generating oscillatory energy of changeable frequency in combination, a 'source of oscillatory energy of fixed frequency, a source of oscillatoryenergy of controllable frequency, a first means controlled 'by said xed frequency source for producing pulses separated by predetermined time intervals of fixed duration, a second means operable to count oi a preset number of applied oscillations and stop, a `coupling between said second means `and said controllable frequency oscillation generator, means including a time delay network and a gating tube in said last named coupling for start" ing vsaid second means to operate a fraction of a cycle after the occurrence of selected ones of said pulses for producing an energy pulse and stopping after said controllable oscillator generates a preset number of cycles, a locking Vcircuit con- ..12 trolled by ,said first =pulses .for producing a first .series of voltages measured by Asaid first time intervals, a second 'locking circuit contrlled Yby oscillatory energies from said controllable source and by the energypulses from said second means for producinga second series o'f voltages measured by said counting periods-means Yfor combining said'voltages to .cancel out those parts ofthe rst and second series of voltages which occur at the same time and leave two resultants, the duration of one v,of which represents the time delayiin starting said second means and the other of which represents 'the time between the end of selected ones of said Atime intervals and the end of the said counting periods, electron discharge means for obtaining the differential of said two resultants and deriving therefrom a potential, the polarity of which is determined by 'which resultant is of greatest duration, and means for controlling the 'frequency of said controllable source in `accordance with said resultant to thereby causesaid .resultant .to have equal lengths.

"5. In .automatic tuning means .for a 4circuit wherein recurring peaks o'f energy liows of a frequency depending on the circuit tuning combination a source of pulse energies of 'xed frequency, alocking circuit triggered Vfrom a condition of rest by one pulse and backftosaid condition of rest by the next pulse, a cycle counter which ,produces pulses a't 'the .end of each count, a gate tube .coupling `said -cycle counter .to said rst circuit, a .locking circuit for opening said `gate by one .of said Afirst pulses Iand .closing said gate by the pulses produced 'by 1said counter, .a third 'locking circuit triggered from rest .condition by peaks of energy passedby .said gate tube and back to said rest condition by 'the pulses produced, and means for comparing the time intervals during which said first and third locking circuits .are out of 'the .rest condition.

6. 'In combination with an oscillation gener ator .having potential-responsive means for stabilizing its output frequency, means for `.applying a first potential to said :stabilizing means, a frequency divider coupled to said generator, means rfor applying vpulses of substantially constant `frequency, a Vfirst element responsive to the rst of said .pulses for producing a second potential, 'second and third elements responsive to said second potential for changing said first potential in one direction and for completing the circuit between said generator and divider after a pre- .determined time delay, a fourth element `responsive to the completion of said circuit vfor stopping said change in said first potential, means including said third and four-th elements Yresponsive to the output of said divider for interrupting .said circuit and changing said ,first potential in the opposite direction,and means including said first element responsive to thesecond of said pulses for stopping the change of .said first potential in said opposite direction.

7. `In combination with .an oscillation gen-era- `tor having potential-responsive means for stabilizing its output frequency, .means for applying a first potential to said stabilizing means, a frequency divider having .an adjustable division ratio coupled to lsaid generator, means for applying pulses of substantially constant frequency, a first element responsive tothe first of said pulses for producing a second potential, second and third elements responsive to .said second potential for changing said rst potential .in one .direction 75 and for .completing the circuit ybetween said gen- MV2 toits other condition of stability whereat current flows in tube 58 and is cut oi in tube 56. This reverses the potentials on the anodes of these tubes so that the potential on the anode of tube 56 rises as represented by line g, Fig. 2-, while the potential on the anode of tube 58 falls as represented by line h, Fig. 2. I have now started the time interval during which I will count the number preset on the device 4. The circuit stands as it has been tripped until the next negative pulse (line a, Fig. 2) is applied from the divider 3 by condenser 26 to the control grids of the tubes 45 and 48 of locking circuit MVI. The tube 45 is drawing current so that its anode makes the grid of tube 48 negative and the said negative pulse is ineffective on this tube. However, the grid of tube 45 is more positive and the negative pulse applied thereto reduces the current in this tube to flip the circuit back to its original starting condition with current flowing in tube 48 and current cut off in tube 45. This, then, has completed the fixed interval of time and the voltage generation by stage MVI during that time is completed as illustrated in lines e and f of Fig. 2.

When the count, which has been going on, is completed, a positive pulse is supplied on lead 44 and makes tube 63 conductive to cause the potential on the anode thereof to fall. This potential has been designated d and is represented in line d of Fig. 2. This negative potential operates to perform two functions. First, it is applied by coupling condenser 65 to the grid of tube 58, then conductive (line g, Fig. 2), to cut oi current flow in this tube and to set up current ow in tube 56 to trip this locking circuit MV2 back to its starting condition and to complete generation of the voltages g and h (Fig. 2) which takesplace during the time interval required to make the preset count. The voltage drop on the anode of tube 63 also reduces the current flow in the cathode follower stage tube CS to cause a fall in the potential on its cathode and to apply a negative pulse through condenser 59 to the control grid of tube 52 of the locking stage MVS. Before application of this potential, current is flowing in the tube 52 and this current flow is now cut-off and current flow in the tube 53 is set up so that this locking circuit is tripped back to its original condition to apply a negative potential to the third grid in the gate tubes 55 to block oscillations and prevent oscillating peak voltages of the frequency of said oscillations from reaching the counter circuit by way of lead 6|. Thus, a complete cycle of operation has been carried out and the circuits for doing the same have been returned to the initial starting position in order that the operation may be repeated which it is on the appearance of alternate pulses from the device 3. Note that one pulse starts the operation by tripping stage MVI out of its rest condition and the next pulse trips MVI back to its rest condition so that cycle counting takes place only during alternate periods of the timer output.

The voltage f on the anode of tube 45 is added to the voltage y on the anode of the tube 56 and supplied by lead 80 to the grid of the combining tube E6. The voltage e on the anode of tube 48 is combined with a voltage h on the anode of tube 53 and supplied by lead 82 to the grid 68. Note that in both combinations, the poten tials are opposed so that in effect, the control grid of tube 66 is excited by the potential represented in line z' while the con-trol grid of tube 68 is excited by potential represented in linea' of Fig. 2. Voltages f and g are combined by i resistors R6 and R6 while voltages e and h are combined by resistors R1 and R1. The voltages as applied to the triodes 66 and 68 vary the potential on the storage condenser C2 of network FN about a base value depending on whether the counting time interval is longer or shorter than the fixed time interval set by the device 3. It will be noted in the embodiment disclosed that positive potentials are used and as a consequence, potentials designated 29 and 30 only of lines i and 7' of Fig. 2 are used. In other embodiments, the negative potentials 29' and 30 may be used or a positive and negative potential may be used. In the embodiment described, the arrangement is such that the potential 29 acting through lead 82 on the grid of tube 68 makes this tube conductive to permit a small amount of the storage charge in the condenser C2 to leak off. The pulse 30 acting through lead 80 on the grid of tube 66 causes this tube to draw current or pass current to permit a small amount of charge to be added to the charge on condenser C2. The net charge on this condenser and hence, its voltage at any time depends on the relative lengths of correction pulses 29 and 3e. In the example given, the frequency of the master oscillator is slightly low so that the time to make the count of the preset number is slightly longer than the standard interval and pulse 36 is longer than pulse 29. Pulse 30 supplies charge to the condenser so that the net charge thereon goes up as does the potential supplied to the reactance tube in unit 6. The reactance tube then might be inductive in character and have its reactive eiect reduced by this increased potential to increase the frequency of operation of the master oscillator to bring it exactly to the frequency preset.

If the master oscillator is exactly on frequency, pulses 29 and v3l) will have the same length and the net correction will be Zero. Then the potential on the ycondenser will be of a Value such as to establish a reactive effect which acts on the master oscillator to cause it to operate at the exact frequency.

Because of the time delay introduced before the counting timer starts, phase variations between the oscillatory energies generated by the source 2 and source I are ineective to reduce the accuracy of operation since the results thereof appear in both pulses 29 and 3] and cancel each other out in the control potential produced at the condenser C2.

What is claimed is:

l. In apparatus for producing oscillatory er1- ergy the frequency of which may be set at any one of numerous frequencies in a wide range of frequencies in combination, a source of oscillatory energy of xed frequency, a source of oscil latory energy of controllable frequency, means controlled by the source of xed frequency for setting up pulses of energy separated by time intervals of fixed duration, a variable frequency divider, means controlled by said iixed frequency source and operating after a time delay for coupling said source of controllable oscillations to said variable frequency divider for counting olf a preset number of cycles of the oscillations generated, means for developing a voltage representative of said time delay, means for developing a voltage representative of the time said variable frequency divider is operating after the ending of said time intervals of xed duration and means for controlling the frequency of said second erator and divider after a predetermined time delay, a fourth element responsive to the completion of said circuit for stopping said change in said iirst potential, means including said third and fourth elements responsive to the output of said divider for interrupting said circuit and changing said first potential in the opposite direction, and means including said rst element responsive to the second of said pulses for stopping the change of said first potential in said opposite direction.

8. In combination with an oscillation generator having potential-responsive means for stabilizing its output frequency, energy storage means for applying a rst potential to said stabilizing means, a frequency divider coupled to said generator, means for applying pulses of substantially constant frequency, a first element responsive to the first of said pulses for producing a second potential, second and third elements responsive to said second potential for changing said first potential in one direction and for completing the circuit between said generator and divider after a predetermined time delay, a fourth element responsive to the completion of said circuit for stopping said change in said first potential, means including said third and fourth elements responsive to the output of said divider for interrupting said circuit and changing said first potential in the opposite direction, and means including said rst element responsive to the second of said pulses for stopping the change of said rst potential in said opposite direction.

9. In combination with an oscillation generator having potential-responsive means for stabilizing its output frequency, means for applying a rst potential to said stabilizing means, a frequency divider coupled to said generator, means for applying pulses of substantially constant frequency, a trigger circuit responsive to the first of said pulses for producing a second potential, first and second elements responsive to said second potential for changing said first potential in one direction and for completing the circuit between said generator and divider after a predetermined time delay, a third element responsive to the completion of said circuit for stopping said change in said first potential, means including said second and third elements responsive to the output of said divider for interrupting said circuit and changing said first potential in the opposite direction, and means including said trigger circuit responsive to the second of said pulses for stopping the change of said first potential in said opposite direction.

10. In a combination with an oscillation generator having potential-responsive means for stabilizing its output frequency, means for applying a first potential to said stabilizing means, a frequency divider coupled to said generator and having an adjustable division ratio, means for producing pulses of substantially constant frequency, a first trigger circuit responsive to the first of said pulses for producing a second potential, means responsive to said second potential for changing said first potential in one direction, means including a second trigger circuit responsive after a predetermined time delay to complete the connection between said generator and divider, means including a third trigger circuit responsive to the completion of said circuit for interrupting said change in said iirst potential, means including said second and third trigger circuits responsive to the output of said frequency divider for interrupting said connection and changing said first potential in the opposite direction, and means including said first trigger circuit responsive to the second of said pulses for stopping said change of said rst potential in said opposite direction.

WARREN H. BLISS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,250,284 Wendt July 22, 1941 2,384,379 Ingram Sept. 4, 1945 2,403,918 Grosdo July 16, 1946 2,420,200 Schoenfeld May 6, 1947 

